The present invention relates generally to a dye laser oscillator including a number of cooperating components for producing a tuned dye beam and more particularly to a specific structural arrangement between these cooperating components and a specific grating assembly which serves as a coarse tuning mechanism in the production of the ultimately tuned beam.
A typical dye laser oscillator includes, among other components, a dye cell assembly, a beam expander, an etalon, a grating assembly, and an output coupler which supports an end mirror. A pump laser beam, for example a copper vapor laser beam, is directed into the dye cell which is designed to receive a continuous supply of dye therethrough. This produces a dye beam which is directed through the beam expander, the latter serving to expand the beam in one direction as much as forty fold, whereby to produce a ribbon of light. This ribbon passes through the etalon and on to the grating which directs a beam (actually a portion thereof) back through the etalon, the beam expander and into the dye cell where it is amplified before finally impinging on the end mirror of the output coupler. A portion of this beam passes through the end mirror and forms the ultimately produced output of the overall oscillator. The rest of the beam is reflected back into and through the dye cell where the process is repeated for purposes of amplification. The etalon and grating assembly serve to limit the ultimately produced beam to a particular narrow wavelength band, the grating serving as a coarse tuning mechanism and the etalon serving as a fine tuning mechanism.
In a dye laser oscillator of the general type just described, it is desirable to minimize the path length taken by the beam within the cavity between its endmost components, specifically its output coupler and grating assembly. This requires a rather compact design. At the same time, it is desirable to be able to readily remove any one of the recited components making up the oscillator without interference from or interfering with the other components. As will be seen hereinafter, the present invention provides an uncomplicated and yet reliable means of accomplishing this.
As stated above, one of the specific components making up the general type of dye laser oscillator is a grating assembly which serves as a coarse tuning mechanism in the production of the ultimately tuned beam leaving the oscillator. In order to accomplish this, the grating assembly includes a grating having an active grating face through which the dye beam is intended to reflect off of dispersing the beam before passing through the laser cavity and leaving the oscillator as well as means for varying the angle at which the beam impinges the grating face which, in turn, varies the wavelength band of the beam. Heretofore, the grating assembly was supported at its end closest to the base for vertical rotation such that this movement took place about a vertical axis by means of a single vertical shaft supported by two tapered roller bearings, thereby leaving the top end of the grating assembly unsupported. This was found to be relatively unstable from a structural standpoint. As will be seen hereinafter, the present invention eliminates this structural instability.
Still referring to the grating assembly forming part of the overall dye laser oscillator of the prior art, it has been found that proper alignment of this component with the intended beam path of the oscillator is critical. This criticality has not been designed into the grating assembly heretofore but does appear in the present invention, as will be seen.